Asymmetrical half-bridge converter with reduced DC-offset current in transformer

In this paper, a new asymmetrical half-bridge converter with reduced DC-offset current in transformer is proposed. In general, to meet the hold-up time conditions, the conventional asymmetrical half-bridge (AHB) converter operates in wide-input-voltage range. Wide-input-voltage range design makes converter suffered from severe asymmetric operation under the nominal operation, which increases the DC-offset current in the transformer, size of the transformer, and unbalance of the voltage stresses of the secondary rectifiers. On the other hand, the proposed converter can reduce the DC-offset current in the transformer and relieve the unbalanced voltage stresses of the secondary rectifiers under the nominal operation by changing transformer turns-ratio with an auxiliary switch and capacitor. Therefore, the proposed converter can achieve high efficiency. The validity of the proposed converter is confirmed by experimental results from a prototype with 330-400V input, 300W/12V output.